In the cleaning process, which is a part of an electrophotographic printing process, the untransferred toner is removed from an image carrier. In order to facilitate the removal of the toner by increasing the releasing property of the toner from the image carrier, or in order to decrease abrasion on a surface of the image carrier (photoreceptor) and a cleaning blade used for cleaning the image carrier, it has been disclosed a method of using a fatty acid metal salt as a lubricant. The fatty acid metal salt is scratched with a device such as a coating brush, and the scratched powder is supplied to the surface of the photoreceptor.
However, with the configuration as described above, there may be produced variation of an amount of the supplied lubricant in the longer direction of the photoreceptor. This is caused by the following reason. When there are locally a high crystalline portion and a low crystalline portion inside of the solid fatty acid metal salt, the high crystalline portion has high hardness, and the low crystalline portion has low hardness. An amount of scratching at the low crystalline portion will be large. When the amount of supplying is varied, the amount of coating of the lubricant will be uneven, and the uneven coating of the lubricant will be visually confirmed as image density unevenness.
Patent document 1 (JP-A No. 2007-224137) discloses a method in which a resin fine powder such as an acrylic resin powder or an inorganic powder such as titanium oxide powder is used together with the fatty acid metal salt. By this, the crystal growth of the fatty acid metal salt is suppressed and the uniform hardness is achieved. Thus, the variation of the amount of the supplied lubricant is restrained.
However, the lubricant described in the Patent document 1 exhibited insufficient effect for restraining unevenness of the amount of the supplied lubricant that was generated by detachment of the lubricant from the surface of the photoreceptor. More specifically, the lubricant will be detached when a scratching force is applied to a surface of a photoreceptor drum in the developing-, transferring-, or cleaning step of an electrophotographic process. In particular, at a portion of a high printing ratio having a large amount of toner in the image surface, the scratching force becomes relatively larger compared with a portion of a low printing ratio having a small amount of toner. The lubricant will be easily detached, and there will be produced abrasion unevenness caused by variation of amount of the detached lubricant. As a result, when images having a large difference in printing ratio in the image surface are continuously printed, it will be produced uneven coating of the lubricant on the photoreceptor according to the printing history. Thus, it will be produced a problem that uneven coating of the lubricant will be visually confirmed as image density unevenness.
Against this problem, there is no improving way by using the lubricant of the Patent document 1. In addition, the lubricant will be detached from the photoreceptor by the fine powder that works as an abrasive agent. Consequently, it may generate the case which increases uneven coating of the lubricant caused by uneven abrasion.